Astronomers are particular people, but few are more particular than the members of the International Astronomical Union. The IAU dictates everything from whether or not something qualifies as a planet, to what that planet (or non-planet) can be called.

The IAU is also in charge of something called planetary nomenclature, or the official names that astronomers bestow on landmarks or features on the surfaces of cosmic objects. The rules of planetary nomenclature are extensive, and surprisingly specific. Here ten of the most interesting, peculiar, and contradictory rules of the lot.

10. Keep Things Apolitical According to the IAU's most basic list of Rules and Conventions, "no names having political, military or religious significance may be used." The reasoning behind this seems pretty obvious. Naming a planetary feature after something with inflammatory potential is never a good idea. Besides, that'swhatwehaveairports for.

9. Unless it's old politics. Or old gods. Political figures from "prior to the 19th century"? Totally fair game — as is pretty much any god from a religion that has a) died out, or b) isn't widely practiced. Examples of this exception abound. Think about it: every planet in our solar system (save for Earth) is named after a Greco-Roman god or goddess. Deities are used for nomenclature purposes all the time. Some of these gods can be pretty obscure, but that doesn't mean there aren't people who care about the use of their names. Which is why:

8. It's Nice to Ask Permission This is probably something of an unspoken rule, but it's definitely the right thing to do. The IAU maintains that any object in the Kuiper belt must be named after a creation deity. When Mike Brown (the astronomer famous for killing Pluto), and his colleague Chad Trujillo discovered an object in the Kiuper belt that was half the size of what was once our solar system's ninth planet, they named it "Quaoar," after an important figure in the creation myth of California's Tongva tribe, which still exists today. In instances like this, astronomers should feel compelled to ask permission to use the name. Writes Brown:

We didn't know anyone in the Tongva tribe, but Chad went to www.tongva.com, found a phone number, and called it. The chief answered. Chad said something like, "Hi, I'm an astronomer from Caltech, and we just discovered something big in this region of space called the Kuiper belt and were hoping to name it after a Tongva creation myth and wanted to talk to you about it," at which point the chief probably thought there was a pretty good chance that Chad was a lunatic rather than an astronomer from Caltech. Perhaps to hedge his bets, or perhaps just to get rid of Chad as quickly as possible, he gave the name of the tribal historian and chief dancer, who would be a better person to talk to about such matter.

Chad made the next phone call. After Chad convinced the tribal historial that he was not a crazy person but was indeed an astronomer who had found something half the size of Pluto that needed a name, the Tongva agreed that Kwawar — or rather Quaoar, their preferred spelling — was the appropriate name.

7. Being Commemorated is Hard To have your name officially considered for commemoration in the form of a planetary feature, the IAU advises you to be "of high and enduring international standing." You also have to be dead (for at least three years).

6. Some of the Best Names Aren't Even Official Plenty of cosmic objects and features go by unofficial names before they're officially recognized. Eris — the dwarf planet, also discovered by Mike Brown, that helped shove Pluto off the precipice of planethood — went by "Xena" (after TV's warrior princess) before it went by its official designation.

Likewise, the IAU states that "features whose longest dimension is less than 100 meters are not assigned official names unless they have exceptional scientific interest." The result is a long list of small planetary features with unofficial nicknames chosen by members of the teams responsible for finding them. For an idea of the kinds of names team members come up with, check out this extensive list of rocks on Mars. Highlights include "Space Ghost," "Zorak," "Marvin the Martian," "Darth Vader" 'Indiana Jones" and "Cookies N Cream."

5. Small Crater, Small Village Martian craters measuring less than 60 km in diameter must be named after villages of the world with a population smaller than 100,000 people. This is the rule that gives us such excellent names as the adorable-sounding and strangely fitting "Tooting crater," named after the eponymous London suburb. (There is no mention of what happens when a town grows to a population of more than 100,000, but the logical conclusion is that we either blow the crater up, or force people to leave the village. DO NOT QUESTION THE IAU ABOUT ITS RULES.)

4. Big Valley? Just Call it Venus. Venusian valleys more than 400 km long are simply called "Venus," but in a different language. This is where we get awesome sounding feature names like Apisuahts Vallis (Apisuahts being the Blackfoot/Algonquin name for planet Venus); Citlalpul Vallis (Aztec for planet Venus); and Kallistos Vallis (Ancient Greek name for planet Venus). Smaller vales, in contrast, are named after river goddesses.

3. Otherwise, Size Doesn't Matter Generally speaking, the IAU naming rules for a planetary feature remain the same regardless of its size; the valleys and craters of Venus and Mars are the exceptions to this rule.

2. No Penis on Venus Every single part of Venus — from tesserae, to chasmata, to the planet itself — must be named after a woman. If you want a feature on the Morning Star named in your honor, you'd better not have a todger in tow.

1. …Unless it's Old Penis The one exception to the moratorium on male members? Maxwell Montes, named after James Clerk Maxwell, which was approved in the late 70s — before the female-only Venutian naming rules came into effect. The other two notable exceptions to the rule are Alpha Regio and Beta Regio, two formations named after the first letters of the Greek alphabet. They, too, were named before the convention of female names was adopted.